Since we are adding the outputs of three oscillators, each with the same amplitude envelope, we'll scale the amplitude before we mix them. Both "iscale" and "inote" are arbitrary names to make the design a bit easier to read. Each is an i-rate variable, evaluated when the instrument is initialized.
instr 4 ; toot4.orc
iamp = ampdb(p4) ; convert decibels to linear amp
iscale = iamp * .333 ; scale the amp at initialization
inote = cpspch(p5) ; convert "octave.pitch" to cps
k1 linen iscale, p6, p3, p7 ; p4=amp
a3 oscil k1, inote*.996, 1 ; p5=freq
a2 oscil k1, inote*1.004, 1 ; p6=attack time
a1 oscil k1, inote, 1 ; p7=release time
a1 = a1 + a2 + a3
out a1
endin
f1 0 4096 10 1 ; sine wave
;instr start duration amp(p4) freq(p5) attack(p6) release(p7)
i4 0 1 75 8.04 .1 .7
i4 1 1 70 8.02 .07 .6
i4 2 1 75 8.00 .05 .5
i4 3 1 70 8.02 .05 .4
i4 4 1 85 8.04 .1 .5
i4 5 1 80 8.04 .05 .5
i4 6 2 90 8.04 .03 1
e